1. Field of the Invention
The present invention relates to a plasma display panel(PDP) device, and more particularly, to a method for controlling a white balance in a plasma display panel device, in which a R(Red) cell, a G(Green) cell and a B(Blue) cell are applied of additional sustain pulses having numbers different from one another after display of one frame of picture to reduce differences of luminances between the R, G, B cells when the same gradation data are provided thereto, for implementation of a stable white balance.
2. Discussion of the Related Art
Referring to FIG. 1, a conventional plasma display panel device includes a plasma display panel 1 having a plurality of address electrode lines and first and second sustain electrode lines disposed thereon, a controlling part 2 for generating digital R, G, B video data(gradation data) to be provided to the plurality of address electrode lines, first and second sustain pulses to be provided to the first and second sustain electrode lines respectively, and different control signals, in response to external signals, address driving parts 3 and 3' each for providing the digital R, G, B video data to the plurality of address electrode lines in response to control signals from the controlling part 2, and first and second sustain driving parts 4 and 5 for providing the first and second sustain pulses to the plurality of first and second sustain electrode lines respectively in response to control signals from the controlling part 2.
Referring to FIG. 2, the plasma display panel 1 includes N numbers of first sustain electrode lines X.sub.1, X.sub.2, - - - , X.sub.N-1, X.sub.N and second sustain electrode lines Y.sub.1, Y.sub.2, - - - , Y.sub.N-1, Y.sub.N formed at fixed intervals alternatively, and M numbers of R, G, B address electrode lines R.sub.1, G.sub.1, B.sub.1, R.sub.2, G.sub.2, B.sub.2, - - - , R.sub.M-1, G.sub.M-1, B.sub.M-1, R.sub.M, G.sub.M, B.sub.M formed at fixed intervals at right angles to the first and second sustain electrode lines X.sub.1 .about.X.sub.N and Y.sub.1 .about.Y.sub.N.
The method for displaying a motion picture or a still picture on the aforementioned plasma display panel with a subfield system will be explained.
The subfield system has an X number of subfields in a frame, with each of the subfields corresponded to one of luminances having relative ratios of 1:2:4:8:16:32:64, - - - , for implementing gray levels of 2.sup.X, thereby a picture corresponding to a number of gradation of 0.about.2.sup.X -1 can be displayed by combining a certain number of the subfields. That is, the controlling part 2 controls the first and second sustain driving parts 4 and 5 to provide reset pulses to the first and second sustain electrode lines X.sub.1 .about.X.sub.N and Y.sub.1 .about.Y.sub.N to make the charges in all the cells in the plasma display panel 1 discharged and erased so that all the cells will not be affected by previous luminescence. Then, the first and second sustain driving parts 4 and 5 provide scan pulses to the first and second sustain electrode lines X.sub.1 .about.X.sub.N and Y.sub.1 .about.Y.sub.N respectively and, on the same time, the address driving parts 3 and 3' provide one bit of digital R, G, B video data to respective address electrode lines R.sub.1 .about.B.sub.M, to excite and make luminous of particular cells to each of which 1(high pulse) is provided as a value of the bit. In general, widths of the reset pulses for discharge and erase of all the cells are narrower than widths of the scan pulses. Next, the controlling part 2 controls the first and second sustain driving parts 4 and 5 to provide first and second sustain pulses as much as a number of first subfields to the first and second sustain electrode lines X.sub.1 .about.X.sub.N and Y.sub.1 .about.Y.sub.N respectively to maintain the luminosity of the particular cells for a predetermined duration required for the first subfields. When the aforementioned steps of discharging and erasing all cells, providing digital R, G, B video data, and providing first and second sustain pulses, are performed repeatedly for the rest of the subfields, one frame of picture can be displayed on the plasma display panel 1.
In the gray scale implementation with the aforementioned subfield system, luminances of the R, G, B cells by the gradation data(digital video data) provided to the R, G, B cells are dependent on numbers of the first and second sustain pulses provided to the plurality of subfields, and a combination of the luminance of the R, G, B cells forms a color of a pixel. In other words, combinations of red, blue, green visible lights emitted at proper luminances from the R, G, B cells in the pixel depending on the digital R, G, B video data(each has a number of bits identical to a number of subfields) provided to address electrode lines Ra, Ga, Ba for the three R, G, B cells for one frame duration implements various colors of the pixel. If the R, G, B cells in the pixel are provided with the same gradation data, white color(achromatic color) is displayed theoretically, and if provided with gradation data different from one another, various colors can be displayed according to ratios of the luminances of the R, G, B cells.
However, because luminous efficiencies of the R, G, B fluorescent materials coated on the R, G, B cells respectively on the plasma display panel are, as known, in general in the order of G fluorescent material&gt;R fluorescent material&gt;B fluorescent material, if discharge space sizes of the R, G, B cells and numbers of the sustain pulses corresponding to the gradation data of the R, G, B cells are the same as the known art, there has been problems that an imbalance in the white balance is occurred such that a greenish white is displayed in an implementation of a white color on a pixel and exact implementations of other colors are not possible because the luminances of the R, G, B cells according to the provided same gradation data are in the order of G cell&gt;R cell&gt;B cell.
And, as can be known from the varied luminances of the R, G, B fluorescent materials depending on the varied current intensities per unit area shown in TABLE 1 below and the R fluorescent material basis relative comparison of the luminous efficiencies of the R, G, B fluorescent materials(also shown by a graph in FIG. 3), because a luminous efficiency of the G fluorescent material increases and a luminous efficiency of the G fluorescent material decreases as a luminance of a screen increases, causing a greater difference between luminances of the G cell and the B cell, as a luminance of a white becomes the higher, the white becomes the more greenish, causing the more serious imbalance in the white balance.
TABLE 1 __________________________________________________________________________ Luminances of R, G, B fluorescent materials according to varied current intensity current intensity (.mu.A/cm.sup.2) 0.9 1.8 2.7 4.5 6.3 9.0 18.0 27.0 36.0 __________________________________________________________________________ Luminance R 1800 3200 4800 7400 10000 12000 23000 32000 40000 (N-T) G 2100 4400 6800 12000 17000 22000 43000 63000 85000 B 600 920 1200 1400 1800 2050 3000 4000 5000 Relative G 1.17 1.37 1.41 1.62 1.7 1.83 1.87 1.96 2.13 ratio B 0.33 0.29 0.25 0.19 0.18 0.17 0.13 0.125 0.11 (R based) __________________________________________________________________________